A conventional off-road vehicle such as a motorcycle is commonly known to have wheel assemblies having an inner tube associated therewith. It is well known that operating such vehicles at low tire pressures (between 4 psi and 10 psi) is advantageous in providing optimal traction. However, at such low tire pressures the tube is often subject to being pinched by deformation of the tire against the rim or by being pinched between the tire bead and the rim. This problem is particularly acute under high performance off-road conditions. Extremely low tire pressures (between 4 psi and 7 psi) are desirable, but not practical as a pinch flat is almost guaranteed. As a result, it is common for such conventional off-road vehicles to operate at higher, less desirable tire pressures (between about 12 psi and 18 psi), in order to eliminate the potential of a flat tire due to tube pinches.
The most common approach to avoid tube pinches is to utilize thick, heavy duty inner tubes under the theory that the additional thickness of the inner tube will better resist tearing/pinching. However, such tubes are still prone to pinching at low or extremely low tire pressure and undesirably add additional weight to the tire assembly. A first approach, as disclosed in U.S. Pat. No. 5,073,444, is to eliminate the tube entirely and insert a generally solid molded foam core that is sufficiently flexible to provide a similar low pressure feel for optimal traction. Michelin and Dunlop corporations offer such foam tire inserts made of closed cell butyl honeycomb foam filled with nitrogen gas having a smooth skin outer surface that must be drenched with a lubricant upon installation. However, such molded foam tire cores are difficult to mount, require a significant amount of lubrication, and add a substantial amount of weight to the tire assembly. They also shrink and disintegrate over time, particularly in extreme high speed competition, requiring frequent replacement. They are also rather expensive, making them generally used by more financially able riders. A second approach, as disclosed in U.S. Pat. No. 6,896,020, is to eliminate the conventional tube and insert a plurality of individually inflated balls into the tire, such that a number of the balls can be pinched without the tire going flat. However, this approach does not provide a simple way to adjust the pressure in the balls to accommodate changes in altitude or temperature, barring complete removal and reinstallation of the balls. Further, installing a plurality of balls into the tire and rim is a challenging process, and combined with their relative expense compared to conventional inner tubes, many riders are discouraged from using them. A third approach, as disclosed in U.S. Pat. No. 7,669,627, is to eliminate the conventional tube and insert a pneumatic sealing ring having an inner tube and expandable liner so that the tire can be inflated like a tubeless tire. However, installing the sealing ring and inner tube can be challenging, and if the bead of the tire or sealing ring is damaged in any way, an air tight seal will not be achieved, resulting in a flat tire. Again, coupled with their relative expense to conventional inner tubes, many riders are discouraged from using them. It should be noted that in the three approaches discussed above, each one of them teaches that to achieve the feel of a low pressurized tire, the conventional inner tube must be eliminated and replaced with something else. None of them address how to eliminate pinch flats incurred by conventional inner tubes.
Therefore, what is desirable is to provide a simple, inexpensive, and easy solution for eliminating tube pinching in conventional off-road vehicles inflated at low tire pressures while keeping the conventional inner tube.
Tire flaps have been used to separate the inner tube from the tire bead and rim for heavy duty motor vehicles. Our research found patents, each of which is cited in an IDS filed concurrently with the application, between the years 1923 and 1956 that teach the use of tire flaps made of vulcanized rubber (or structurally equivalent materials) to protect the inner tube from damage by the rocking of the tire bead, abrasion with the rim, and to prevent entry of foreign material into the rim. Generally, they are a continuous band of solid rubber used in inner tube tire assemblies for vehicles requiring high tire pressures such as between about 35-60 psi. Patents found between the years 1970 to 1984, all of which are cited in the IDS, teach improvements to tire flaps to overcome problems of tube blowouts occurring in tire pressure applications between about 100-110 psi. Again, these teach tire flaps made of generally the same solid vulcanized rubber material as the inner tube, and are only intended to solve the problem of fatigue stress cracks occurring on the inner tube where the tire sidewall deflects somewhat under heavy loads. As will be explained herein, these conventional rubber tire flaps are not designed to prevent pinch flats in off-road vehicles utilizing inner tubes inflated at low tire pressures, nor are they intended for use in such an application.